Gasoline producing process comprising hydrocracking and reforming

ABSTRACT

A COMBINATION PROCESS INVOLVING HYDROCRACKING AND DEHYDROGENATION. HYDROCRACKING OF A HEAVIER-THAN-GASOLINE CHARGE STOCK IS EFFECTED AT CONDITION CONDUCTIVE TO AROMATIC SATURATION AND EXTENDED CATALYST STABILITY. DE HYDROGENATION OF AT LEAST A PORTION OF THE HYDROCRACKED PRODUCT EFFLUENT IS EFFECTED AT CONDITIONS WHICH ARE CONDUCTIVE TO THE CONVERSION OF NAPTHTHENES TO AROMATICS. THE HYDROCRACKING REACTION IS EFFECTED AT HIGH PRESSURES AND HIGH SPACE VELOCITIES, WHILE THE DEHYDROGENATION REACTION IS EFFECTED AT LOWER PRESSURES AND LOWER SPACE VELOCITIES.

United States PatentO ABSTRACT OF THE DISCLOSURE 7Claims A combination process involving hydrocracking and dehydrogenation. Hydrocracking of a heavier-than-gasoline charge stock is effected at conditions conducive to aromatic saturation and extended catalyst stability. De-

hydrogenation of at least aportion of the hydrocracked productefliuent is effected at, conditions which are conducive to the conversion of naphthenes ,to aromatics. The

hydrocracking reaction .is efiected at high pressures and high space velocities, while the dehydrogenation reaction is eifected at lower pressures and lower space velocities. V

iAPPLICABI LITY OF INVENTION v j j The: present invention encompasses a process for converting an aromatic-containing hydrocarbonaceous charge stock into lower-boiling hydrocarbon products.

More specifically, the present invention is directed toward a combination process for the production of a high octane gasoline boiling range product from hydrocarbonaceous material boiling at temperatures exceeding the normal gasoline boiling range, which combination process inv volves hydrocracking followed by dehydrogenationnParticularly advantageous is the application of the present combination process to the conversion of charge stocks boiling .at temperatures exceeding the normal kerosene boiling range-Le. from about 550 F. to about 950 .F.

where it may, be desired to maximize the production of both kerosene boiling range fractions and high octane gasoline boiling. range fractions.

Extensive investigations into the. problems attendant economically acceptable hydrocracking processes have indicated that the presence of nitrogenous and sulfurous compounds, regardless of the precise boiling range thereof, results in the deactivation of the catalytically active metallic component. These investigations have further indicated that the adverse effect of nitrogenous compounds is significantly more deleterious than the adverse effect of the sulfurous compounds. As a result of these investigations, hydrorefining techniques have been suggested and developed as a means for pretreating the charge stock for, the purpose of eliminating and/ or decreasing the concentration of the nitrogenous and sulfurous compounds. Provisions, are, therefore, made to eliminate and/orv decrease the concentration of the nitrogenous and sulfurous compounds prior .to bringingthe hydrocarbonaceous charge stock into, contact with thehydrocracking catalyst. In view of the abundance of prior art directed at hydrorefining processes, and since the-pretreatment of the feed forms no essential part of our invention, .for the purposes of further illustration, it will be assumed that the charge naphthalene, anthracene, pyrene, triphenylene, etc., as well as a wide variety of alkyl-substituted polynuclear aromatic compounds. Deleterious eifects of aromatic compounds within the pretreated charge to the hydrocracking process result from the fact that aromatics appear tobe absorbed on the surface of the catalyst without being either hydrogenated, or cracked, and the catalytic surfaces and centers are actively shielded from the material being processed as a result of the condensation, or polymerization thereof, accompanied by ultimate coke formation. Additionally, the hydrogenation of aromatic'compounds is extremely exothermic, and leads to the possibility of experiencing a temperature run-away. The net result of thetemperature run-away is the unabated conversion of normally liquid hydrocarbons into excessively large amounts of light parafiinic hydrocarbons.

In' accordance with our invention, the hydrocarbonaceo'us charge stock is subjected to hydrocracking at conditions conductive to aromatic hydrogenation, such 'that very little catalytic deactivation is experienced, the risk of run-away temperature is minimized and aromatics are not absorbed on the catalyst surface. These operating conditions include a liquid hourly space velocity greater than 8.0 and a pressure greater than 1,000 p.s.i.g. These conditions permit the aromatic hydrocarbons to become saturated, or hydrogenated, before they can condense on the active surfaces of the catalytic composite. At least a portion of the hydrocracked product eflluent is then subjected to dehydrogenation, at conditions conducive to converting naphthenes to aromatics. These conditions include a liquid hourly space velocity less than 8.0 and a pressure-less than 1,000 p.s.i.g. As hereinafter indicated in greater detail, a preferred technique involves the separation of the hydrocracked product effluent to provide a heavier-than-gasoline boiling range material which is recycled to the hydrocracking reaction zone.

OBJECTS AND EMBODIMENTS A principal object of our invention is to produce a high octane rating gasoline boiling range eflluent. A corollary objective is to convert heavier-than-gasoline charge stocks into lower molecular weight gasoline boiling range produ'cts.

Another object is to provide a combination process in volving hydrocracking and dehydrogenation wherein the catalyst activity and stability is materially improved.

In a broad embodiment, therefore, our invention relates to a hydrocarbon conversion process which comprises the steps of: (a) reacting an aromatic-containing charge stock, boiling above the gasoline boiling range, and hydrogen, in contact with an acidic, Group V'HI noble metal catalyst, and at conversion conditions including a liquid hourly space velocity above 8.0 and a pressure above 1,000 p.s.i.g.; (b) reducing the pressure of at least a portion of the conversion product efiiuent to below 1,000 p.s.i.g.; (c) dehydrogenating said portion of the product efiluent at dehydrogenation conditions including said reduced'pressure and a liquid hourly space velocity below stock intended for hydrocrackinghas been previously submitted to a hydrorefining technique. Further discussion ofhydrorefiru'ng techniques are not, therefore, necessary herein. 1 1 Notwithstanding that the hydrocarbonaceous; material is subjected to. a hydrorefining process, ithas been found that a contaminating influence in,the; form of aromatic compounds remains in the charge stock. In addition to high-boiling, alkyl and aryl-substituted mononuclear aromatic hydrocarbons, such aromatic compounds include about 8.0, in contact with a Group VIII noble metal dehydrogenation catalyst; and (d) separating the resulting dehydrogenated product exfiluent to provide a hydrogenrich vaporous phase and to recover a gasoline boiling range hydrocarbon product. In another embodiment, the conversion conditions include a liquid hourly space velocity of about 8.5 to about 16.0, a pressure of about 1,300 to about 2,000 p.s.i.g., a maximum catalyst bed temperature of about 900 F. and ahydrogen-concentration of about 5,000 to about 25,000 s.c.f./bbl. The dehydrogenation conditions include a preferred pressure in the range of about to about 800 p.s.i.g.', a liquid hourly space velocity of about 2.0 to about 7.5 and preferably from 1.0 to about 5.0, a catalyst bed temperature of about 850 F. to about 1100 F. and a hydrogen concentration of about 5,000 to about 25,000

s.c.f./bbl.

Other objects and embodiments of our invention relate to additional details regarding preferred catalytic ingredients, concentration of components within the catalytic composite, various methods of catalyst preparation, preferred processing techniques and similar particulars which are hereinafter given in the following, more detailed summary of our invention.

SUMMARY OF INVENTION Suitable charge stocks, to which the present invention is applicable, are aromatic-containing, heavier-than-gasoline boiling range hydrocarbon fractions. In employing the term heavier-than-gasoline, it is intended to allude to ahydrocarbon fraction boiling above a temperature of about 400 F. It is recognized that the end boiling point of gasoline fraction varies from about 375 F. to about 425 -F., and is primarily dependent upon custom and useage in a particular locale. No intent is made, therefore, to limit the present invention to a particular end boiling point for the gasoline fraction. Heavier charge stocks include kerosenes, boiling in the range of about 400 .F. to about 600 F.; light gas oils, boiling in the range. of about 500 F. to about 750 F; and, heavier gas oils' boiling up to about 950 F. With some modification, the fresh feed may contain hydrocarbons boiling up to a temperature of about 1050 F. As hereinbefore set forth, the majority of charge stocks, intended for hydrocracking, are contaminated by sulfurous compounds and nitrogenous compounds, and it will be presumed that the various feed stocks have been subjected to a prior clean-up operation before being charged to the hydrocracking process encompassed by our invention.

The operating conditions, under which the process is conducted, will generally vary according to the physical and chemical characteristics of the charge stock. However, the present invention is founded upon recognizing that increased stability is afforded in a hydrocracking process when utilizing a Group VIII noble metal catalyst to process aromatic-containing feed stocks, and when conversion is effected at elevated liquid hourly space velocities, without an accompanying consequential loss of catalytic activity. Our investigations have indicated that little or no catalyst deactivation is effected at liquid hourlyspace velocities above about 8.0. The preferred range for the LHSV is 8.5 to about 16.0. The pressure imposed upon the hydrocracking reaction zone is greater than. 1,000 p.s.i.g., with an upper limit of about 3,000 p.s.i.g., a preferred range being 1,300 to about 2,000 p.s.i.g. The maximum catalyst bed temperature is 900 F., with the lower limit being about 600 F. The hydrogen concentration will be in the range of 1,000 to about 50,000 s.c.f./bbl., a narrower range of 5,000 to about 25,000 s.c.f./bbl. being preferred. Hydrocracking and hydrogenation reactions are exothermic in nature, and an increasing temperature gradient is experienced as the hydrogen and feed stock traverse the catalyst bed. The maximum catalyst bed temperature should be maintained below a level of 900 E, which temperature is virtually identical to that which may be conveniently measured at the outlet of the reaction zone. In order to insure that the catalyst bed temperature does not exceed the maximum allowed for a given process, the use of conventional quench streams, either normally liquid or normally gaseous, introduced at one or more intermediate loci of the catalyst bed, may be utilized.

The hydrocracking catalytic composite will contain one or more metallic components from the noble metals of Group VIII; specifically, these metallic components are ruthenium, rhodium, palladium, platinum, osmium, and iridium, with platinum and/ or palladium being preferred. Catalytic composites containing these metallic components are prepared by introducing the same into a suitable porous carrier material. Suitable porous carrier materials are those possessing an acid-acting function, and include amorphous refractory inorganic oxides such as alumina (having a halogen combined therewith), Zirconia, silica, alumina-silica, silica-zirconia, aluminia-silica-boron phosphate, etc. When of the amorphous refractory inorganic type, a preferred carrier material constitutes a composite of alumina and silica, with silica being present in an amount of about 10.0% to about 90.0% by weight. In many applications of the present invention, particularly when processing the heavier gas oils, the carrier material will be a crystalline aluminosilicate. This may be naturally-occurring, or synthetically prepared, and includes mordenite, faujasite, Type A or Type U molecular sieves, etc.

Preferred carrier materials have an apparent bulk density of about 0.15 to about 0.70 gm./cc. and surface area characteristics indicating an average pore diameter of about 20 to about 300 angstroms, a pore volume of about 0.10 to about 1.0 mL/gm. and a surface area of about to about 700 square meters per grams, or more. The carrier material may be prepared in any suitable manner, and may be formed in any desired shape such as spheres, pills, cakes, extrudates, powders, granules, etc. When a a crystalline aluminosilicate, or zeolitic material, is intended for use as the carrier material, it may be prepared in a number of ways known in the art. One common method is to mix solutions of sodium silicate, or colloidal silica, and sodium aluminate and allow the solutions to react to form a solid crystalline aluminosilicate. In many instances, it is preferred to utilize a preparation scheme which results in substantially pure crystalline aluminosilicate particles. Substantially pure is intended to connote an aggregate particle at least 90.0% by Weight of which is zeolitic. This carrier material is distinguished from an amorphous carrier material, or prior art pills and/or extrudates in which the zeolitic material is dispersed within an amorphous matrix with the result that only about 40.5% to about 70.0% by weight of the final particle is zeolitic.

Regardless of the method employed to combine the Group VIII noble metal components with the carrier material, the final composite will generally be dried at a temperature of about 200 F. to about 600 F., for a period of from 2 to about 24 hours or more, and finally calcined at a temperature of about 700 F. to about 1100 F. in an atmosphere of air, for a period of about 0.5 to about 10 hours. Crystalline aluminosilicate catalysts are prefer ably calcined at temperatures not exceeding 1000 F.

Catalytic composites utilized in the hydrocracking reaction zone will often contain a halogen component. Although the precise form of the chemistry of association of the halogen component with the carrier material and metallic components is not accurately known, it is customary in the art to refer to the halogen component as being combined with the carrier material, or with the other ingredients of the catalyst. The halogen may be either fluorine, chlorine, iodine, bromine, or mixtures thereof, with fluorine and/or chlorine being particularly preferred. The quantity of halogen is such that the final composite contains about 0.1% to about 3.5% by weight, and preferably from about 0.5% to about 1.5% by weight, calculated on the basis of the elemental halogen.

Group VIII noble metal components may be incorporated within the catalytic composite in any suitable manner including coprecipitation or cogellation with the carrier material, ion-exchange, or impregnation. Impregnating techniques, utilizing a suitable water-soluble compound of the Group VIII noble metal, are preferred methods. Typical water-soluble compounds include chloroplatinic acid, chloropalladic acid, ammonium chloroplatinate, platinum chloride, dinitro diamino platinum, etc. The use of a noble metal halide, such as chloropalladic acid, is pre fBIICd SlIlCC it facilitates the incorporation of both the noble metal component and at least a minor quantity of a halogen component in a single step. In addition, it is generally preferred to impregnate the carrier material after it has been calcined in order to minimize the risk of losing the valuable noble metal compound; however, in some instances, it may prove advantageous to impregnate the carrier material while it exists in a gelled state. The final catalytic composite will contain from about 0.01% to about 2.0% by weight of the noble metal component, calculated as the element thereof.

Prior to its use in the hydrocracking reaction zone, the catalytic composite maybe subjected to a substantially water-free reduction technique. Substantially pure and dry hydrogen (less than about 30.0 vol. p.p.m. of water) is utilized as the reducing agent. The calcined composite is contacted at a temperature of about 800 .F. to about 1200 F., and for a period of about 0.5 to about 10 hours, and effective to substantially reduce the metallic components. Reduction techniques may be performed in situas part of a start-up sequence provided precautions areobserved to pre-dry the unit .toa substantially water-free state, and provided substantially water-free hydrogen is employed. 1

Additional improvements are generally obtained when the reduced composite is subjected to a presulfiding operation for the purpose of incorporating therewith from about 0.05% to about 0.50% by weight of sulfur, on an 1 elemental basis. The presulfidin'g treatment is eflfected in the presence of'hydrogen and a suitable sulfur containing compound such as hydrogenv sulfide, lower molecular weight mercaptans, various organic sulfides, carbon disulfide, etc. The preferred technique involves treating the reduced catalyst with 'a sulfiding gas, such as a mixture of hydrogen and hydrogen sulfide with about 10 mols of hydrogen per mol of hydrogen sulfide, and at conditions selected to effect: the desired incorporation of sulfur. It is generally considered a good practice to effect the presulfiding technique under substantially water free conditions. V

At the foregoing conditions of operation, and in the presence of the acidic, noble metal catalyst, substantially all the polynuclear aromatic hydrocarbons and a large prodrogen and light paraflinic hydrocarbons. Any suitable 7 means may be employed toseparate the 400 F.-minus fraction from the hydrocracked product efiluent, one of which involves the use of a hot separator into which'the total efliuent is introduced. The hot separator functions at substantiallythe same pressure, allowing only forthe pressure drop experienced as a result of fluid flow, and at a temperature such that the desired gasoline fraction is recovered. ,'Ihe material heavier than the gasoline fraction is recycled to combine with the fresh hydrocarbon charge stock to the hydrocracking reaction zone, thereby providing a combined liquid feed ratio in the rangeof about 1.1 to about 6.0. I

The charge to the dehydrogenation reaction zone is reduced in pressure to a level below. about 1,000 p.s.i.g., and preferably to a level in the range of from 150 to about.800 p.s.i.g. The temperature is increased to a level required to have catalyst bed temperatures-in the range of from 850 F. to about 1100 F. Since the principal reactions being effected are endothermic in nature, a

decreasing temperat'ure gradient will be experienced as the charge stock and hydrogen traverse the hydrogenation catalyst. Temperature control is efiected by monitoring the temperature at. the outlet of the catalyst bed. The

liquid hourly space velocity is less than 8.0, being from 2.0 to above 7.5 and preferably from 1.0 to about 5.0, and the hydrogen concentration is within the range of from about 5,000 to about 25,000 s.c.f./bbl.

The dehydrogenation catalyst is a non-acidic composite of a Group VIII noble metal component, the latter being ruthenium, osmium, rhodium, iridium, and preferably palladium, or platinum. In utilizing the term non-acidic, it is intended to allude to a catalyst in which well-known ,acidic components are not intentionally added. Thus, it is intended to exclude the use of a carrier material which is an intimate mixture of alumina and silica. Furthermore, it is intendedto preclude the intentional incorporation of halogen components, as well as other inorganic oxides which possess an acidic, function characteristic of material which fosters cracking reactions. The referred carrier material constitutes alumina containing not more than 0.1% by weight of halogen, generally resulting from the use of a halogen compound in the preparation of the alumina or during the incorporation of the metallic components therewith. The Group VIII noble metal components are generally utilized in an amount in the range of from 0.01% to about 2.0% by weight, computed as the elemental metal. In order to neutralize the inherent acidic properties. possessed by the Group VIII noble metals and, to a certain extent, by the alumina carrier material, an alkalinous metal component from the group of calcium, magnesium, strontium, cesium, rubidium, potassium, sodium and. especially lithium is employed. These neutralizing metals 'will be present in amounts in the range of about 0.01% to about 1.5% by weight. Another component of the preferred catalytic composite for use in the dehydrogenation reaction zone is selected from the group of arsenic, antimony and bismuth, in an amount such that the atomic ratio of the Group V-A component to noble metal component is within the range of about 0.20 to about 0.45. Of these, arsenic appears to possess an unusual aflinity for the noble metal such that it remains within the composite for an extended period of time, and is, therefore, preferred. Additional details of this preferred dehydrogenation catalyst, as well as methods of preparation, may be found in US. Pat. No. 3,291,755, issued to Vladimir Haensel, et al.

The effluent from the dehydrogenation reaction zone is utilized as a heat-exchange medium and further cooled to a temperature in the range of about 60 F. to about F. The cooled efiluent is introduced into a high pressure separator which serves to provide a hydrogenrich recycle gas stream, to be combined with the charge to the hydrocracking reaction Zone, and a normally liquid product stream. The latter is introduced into a suitable fractionation/distillation system from which the desired product is recovered. Any hydrocarbons heavier than gasoline, removed in the overhead phase from the hot separator, or other separation means, can be recovered and also recycled to combine with the fresh feed charge stock.

In accordance with our invention, the hydrocarbon charge stock and hydrogen are contacted with a catalytic composite, of the type described, in the respective conversion zone. The contacting may be accomplished by using the catalyst in a fixed-bed system, a moving-bed system, a fluidized-bed system, or in a batch-type operation. In view of the risk of attrition loss of the catalyst, it is preferred to use a fixed-bed system. The hydrogenrich vaporous phase and the charge stock are preheated by' any suitable heating means to the desired initial reaction temperature, the mixture being passed into the reaction zone containing the fixed-bed of the catalytic composite. It is understood, of course, that the conversion zone may consist of one or more separate reactors having suitable means therebetween to insure that the desired conversion temperature is maintained at the entrance to one or more catalyst beds. The reactants may be contacted with. the catalystin either upward, downward or radial flow fashion, with the downward/ radial flow being preferred. Additionally, the reactants may be in the liquid phase, a mixed liquid-vapor phase, or a vapor phase when they contact the catalyst.

EXAMPLE Specific operating conditions, processing techniques, particular catalytic composites and other individual proc ess details will be given in the following description of a preferred embodiment. In presenting this example, it is not intended that our invention be limited to the specific illustration, the particular operating conditions, catalytic composites, processing techniques, charge stocks, etc. Therefore, it is understood that the present invention is merely illustrated by the specifics hereinafter set forth.

The charge stock utilized in presenting this illustration is a full boiling range heavy gas oil having a gravity of 188 API, an initial boiling point of about 650 'F. and an end boiling point of about 1025 F. Su1furous compounds are present in an amount of 600 ppm. by weight, as elemental sulfur, and the gas oil contains about 1,500 p.p.m. by weight of nitrogen. The gas oil, in an amount of 10,500 bbl./day, is initially subjected to a clean-up operation utilizing a catalytic composite of 63/37 alumina/silica (weight ratio) containing about 1.8% by weight of nickel and 16.0% by Weight of molybdenum.

Operating conditions in the clean-up zone include a maximum catalyst temperature of 850 F., representing an increasing temperature gradient of 100 F., a pressure of about 2,100 p.s.i.g., a liquid hourly space velocity of 0.64 and a hydrogen concentration of about 10,000 s.c.f./ bbl. At these conditions, hydrogen consumption is 2.18% by weight of the feed stock, or 1,365 s.c.f./bbl., and a significant degree of conversion into lower-boiling hydro carbons is effected.

The hydrocracking zone is intended to function in series-flow with the clean-up zone; therefore, the total effiuent from the latter is introduced into the former without intermediate separation. Hydrocracking conditions include an LHSV of about 8.5, a maximum catalyst ternperature of about 830 F., representing an increasing temperature gradient of about 50 F., controlled by. a hydrogen quench stream in an amount of 3,900 s.c.f./bbl., and a pressure of about 2,000 p.s.i.g. Hydrogen consumption, in the hydrocracking reaction zone, is 1.64% by weight of the feed stock, or 1,025 s.c.f./bbl.

The hydrocracking catalyst is a composite of 0.75% by weight of platinum, about 0.8% by weight ofcombined chloride and a faujasitic crystalline aluminosilicate, 91.9% by weight of which is zeolitic.

Overall product yield and distribution is presented in Table I, and includes the total hydrogen consumption of 3.82% by weight,'or 2,390 s.c.f./bbl. That portion of the product eflluent boiling above 400 F. is separated and recycled to combine with the charge to the hydrocracking zone, providing a combined liquid feed ratio of 1.6.

TABLE I.HYDROCRACKING PRODUCT YIELD AND DISTRIBUTION Pertinent properties of the heptane-400 F. fraction and the combined pentane/hexane fraction are presented in the following Table II.

The efiluent from the hydrocracking reaction zone is introduced into a hot separator at a pressure of about 1,950 p.s.i.g., and a temperature selected to enable separation of the eflluent to provide a bottoms recycle stream substantially free from 400 F.-minus hydrocarbons. The overhead stream is treated for ammonia and hydrogen sulfide removal, and is introduced into a dehydrogenation reaction zone at a pressure of about 300 p.s.i.g. and a catalyst bed inlet temperature of about 980 F. The catalyst is a composite of alumina, 0.5% by weight of lithium, 0.75 by weight of palladium and arsenic in an atomic ratio to palladium of about 0.31.

With respect to the pentane/hexane fraction, it will be noted from Table I that the volume ratio of iso-pentane to n-pentane is about 93.3/ 6.7. Significantly, iso-pentane is unaffected in the dehydrogenation zone, and thus contributes significantly to the octane rating of the ultimate liquid product. Hexanes are also substantially unchanged, but the naphthenes will be dehydrogenated to benzene.

Respecting the heptane-400 F. fraction, the greater portion of the naphthenes will be dehydrogenated, and a significant degree of paraffinic dehydrocyclization is effected. The latter is a surprising result in view of the lack of an acidic-function on the catalyst. Pertinent product properties are presented in the following Table III.

TABLE III.DEHYDROGENIA'ISION PRODUCT PROPER- T E The foregoing illustrates the techniques of effecting the combination process of our invention and the benefits afforded through the utilization thereof.

, We claim as our invention:

1. A process for the conversion of a hydrocarbon charge stock consisting essentially of heavier-than-gasoline hydrocarbons and containing aromatic hydrocarbons in an amount having a deleterious effect on hydrocracking catalysts, said process comprising'the steps of:

(a) reacting said aromatic-containing charge stock,

boiling above the gasoline boiling range, and hydrogen, in contact with an acidic, Group VIII noble metal catalyst, and at hydrocracking and aromatic saturation conditions including a temperature of from about 600 F. to about 900 F., a liquid hourly space velocity above 8.0 and a pressure above 1,000 p.s.i.g. to convert aromatics to naphthenes;

(b) reducing the pressure of at least a portion of the conversion product effluent to below 1,000 p.s.i.g.; (c) dehydrogenating said portion of the product effiuent at dehydrogenation conditions including a temperature of from about 850 F. to about 1100 B,

said reduced pressure and a liquid hourly space velocity below about 8.0, in contact with a Group VIII noble metal dehydrogenation catalyst to dehydrogenate 'naphthenes contained therein; and,

(d) separating the resulting dehydrogenated product efiluent to provide a hydrogen-rich vaporous phase and to recover a gasoline boiling range hydrocarbon product.

2. The process of claim 1 further characterized in that said hydrocracking and aromatic saturation conditions in- 9 clude an LHSV of about 8.5 to about 16.0, a pressure of about 1,300 to about 2,000 p.s.i.g., and a hydrogen concentration of about 5,000 to about 25,000 s.c.f./bbl.

3. The process of claim 1 further characterized in that said dehydrogenation conditions include a pressure of about 300 to about 800 p.s.i.g., an LHSV of about 2.0 to about 7.5, and a hydrogen concentration of about 5,000 to about 25,000 s.c.f./bbl.

4. The process of claim 1 further characterized in that the conversion product efiluent is separated to provide (1) a gasoline boiling range liquid stream and (2) a heavier-than-gasoline boiling range liquid stream, and said gasoline boiling range stream is reduced in pressure and said heavier-than-gasoline boiling range stream is recycled to combine with said charge stock.

5. The process of claim 1 further characterized in that said acidic catalyst is siliceous, and said dehydrogenation catalyst is a composite of neutralized alumina and a Group VIII noble metal component.

6. The process of claim 5 further characterized in that 10 said acidic catalyst is a composite of an alumina-silica carrier material and a platinum or palladium component. 7. The process of claim 5 further characterized in that said dehydrogenation catalyst is a composite of alumina, a platinum component or a palladium component, and an alkalinous metal component.

References Cited UNITED STATES PATENTS 3,409,539 11/1968 Paterson 208-60 2,651,598 9/1953 Ciapetta 208-138 FOREIGN PATENTS 547,016 10/ 1957 Canada 20860 HERBERT LEVINE, Primary Examiner US. Cl. X.R. 

